NMR probe having an inner quadrature detection coil combined with a spiral wound outer coil for irradiation

Abstract

A high resolution NMR probe having two or more resonators, an inner resonator which is closely coupled to a sample and is used to stimulate and receive a response from one nuclear species, and an outer resonator to induce transitions in another nuclear species, wherein the resonators may be provided with cooling capability and may be made of superconducting material, and wherein the inner resonator may be a saddle coil or a birdcage coil with capability of being tuned, and wherein the outer resonator may be one or more spiral wound saddle coil.

Description

BACKGROUND OF THE INVENTION1. Field of InventionThis invention relates to a nuclear magnetic resonance (NMR) probe and magnetic resonance imaging (MRI) utilizing radio frequency (RF) signals; and more particularly, to such a probe having an inner detection resonator combined with an outer resonator consisting of a spiral irradiation coil to thereby minimize the mutual inductance between the two resonators. Sensitivity is improved by means of an inner resonator consisting of a birdcage coil or dual saddle coils operated in the quadrature mode. Further sensitivity enhancement is obtained by cooling the resonators, or by fabricating one or more of the resonators from a superconductive material and operating in the superconducting temperature region.2. Related ArtThe following disclosures show related art:1. U.S. Pat. No. 6,100,694, Aug. 8, 2000, W. H. Wong.2. U.S. Pat. No. 6,420,871, Jul. 16, 2002, W. H. Wong, S. Uno, and W. Anderson.3. U.S. Pat. No. 4,694,255, Sep. 15, 1987, C. E. Hay...

AI Technical Summary

Benefits of technology

A further object is to improve the reliability, power efficiency, and sensitivity of the RF probe used in NMR systems.

The foregoing and other objects are attained by the invention, which encompasses a unique and novel structure RF probe, for example, used in an NMR system, wherein a cylindrical birdcage coil is configured to have a capacitor toward one end portion thereof comprising a conductive ring disposed within or outside the birdcage, which is circumferentially or axially mutually movable to selectively control the frequency of the birdcage coil. The birdcage coil may be configured of a plurality of parallel straight legs, or tapered legs, extending from a conductive ring. The probe may also combine the birdcage with a spiral coil, which in operation is not inductively coupled to the birdcage coil. The birdcage coil and / or spiral coil may be cooled to a low temperature so as to increase the sensitivity and increase the power efficiency.

Problems solved by technology

Normally, only one outer coil is used as additional saddle coils would strongly couple together or couple to the inner saddle coil, thus resulting in a loss of sensitivity and an increase of complexity in tuning the individual coils.

The process of double tuning decreases the efficiency of the coils, thereby requiring more drive power to cause the desired nuclear resonance transitions.

Accordingly, it can be appreciated that the related prior art does not provide a multifrequency tuned quadrature probe design for an RF probe which has high resolution and with capacity for multifrequency decoupling.

Moreover, the art is lacking such a probe, which has excellent sensitivity and efficient RF power usage and simplicity in structure.

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